The surface modification of carbonaceous compounds and materials has been widely explored as a means for achieving desired chemical and physical properties not normally exhibited by carbonaceous compounds and materials. Specifically, the introduction of sulfonate substituents, which are hydrophilic in nature, has been perceived as a potential means for enhancing the self-dispersibility and long-term stability of carbonaceous compounds and materials. Traditionally, various additives, dispersants and surfactants were used to improve the dispersibility and long-term stability of carbonaceous compounds and materials in waterborne systems. However, these materials only show marginal improvement in the dispersibility and stability of such carbonaceous compounds. Additionally, such additives can increase the viscosity of a dispersion, which would be undesired for particular end uses such as ink dispersions and, in particular, ink jet formulations. Moreover, these additives add significant costs and are therefore economically unfavorable as well.
To this end, several attempts have been made at sulfonating carbonaceous compounds and materials. However, these existing methods similarly produce, at best, undesired and marginal results. Specifically, the processes of the prior art present a considerable problem in that it is extremely difficult to avoid oxidation of a carbonaceous compound or material and the subsequent formation of tarry byproducts during the sulfonation reaction. Therefore, it is one object of the present invention to provide an improved process for the formation of sulfonated carbonaceous compounds and materials that substantially minimizes the oxidation of the carbonaceous compound(s) and formation of undesired and problematic tarry byproducts.
Additionally, the processes of the prior art only succeed in providing sulfonated carbonaceous compounds and materials having a minimal degree of surface substitution. To that end, it is a further object of the present invention to provide sulfonated carbonaceous compounds and materials having a surprisingly substantially improved degree of surface modification and thereby resulting in superior dispersibility and long-term stability in waterborne systems.